1. Field of the Invention
The present invention relates to a printing method and apparatus which receives print data from an information processing apparatus and can perform printing on both sides of a recording medium. The invention also relates to an information processing apparatus which communicates with the printing apparatus to enable transmission the print data.
2. Description of the Related Art
In recent years, with printing apparatuses (printers) being used as output apparatuses for computers, many printers have been proposed with double-sided printing capability, in which printing is automatically performed on both sides of a sheet of paper. Double-sided printing saves energy and paper.
Generally, a printer having a two-side printing function has only one printing apparatus. In this printer, one-side printing is performed, the sheet of paper is inverted by a paper convey unit and then fed to the printing apparatus again, and the back of the sheet is printed, thereby making it possible to perform two-side printing.
In the printer described above, to avoid delaying conveyance of the paper during inversion by the paper convey unit, the following method is used. Instead of printing the back of a certain sheet of paper after the front of the sheet is printed, the front of the next sheet is printed while the preceding sheet is inverted, and then the back of the inverted sheet is printed. This method reduces or eliminates the delay caused by conveyance of the paper during inversion by the paper convey unit. In this case, the front of the next sheet of paper having a higher page number may be performed before the back of the preceding sheet having a smaller page number.
To ensure correct page order is maintained with the above method, the following method may be used. The back of a sheet is printed before the front to correctly arrange the page order, and the front of the sheet is printed after inversion, thereby correctly arranging the page order.
In this case, the back of a sheet having a higher page number may be printed prior to printing the front of a sheet having a smaller page number.
However, since page data constituted by a plurality of pages sent from a host computer are sent in an ascending order or a descending order unless a user specifies the order, the following method is used. That is, when the page numbers of pages to be actually printed are replaced with each other, page data of a page which has not been printed is stored in the printer, and the page data of the next page is extracted from the host computer to perform printing. Thereafter, printing of the page is performed on the basis of the page data which has been stored. For this reason, a storage unit for temporarily storing page data is required. This raises the cost of the apparatus.